Pressure sensitive adhesives are materials which adhere to a surface, such as skin, with slight pressure. Desirably, the adhesive subsequently can be released from that surface both without damaging or, if the surface is skin, causing pain to, the surface and without leaving an adhesive residue on the surface. Numerous pressure sensitive adhesives have been developed that are effective for a day or two, such as bandages to cover skin wounds or abrasions, or transdermal patches that deliver a drug or other therapeutic agent to or through the skin. In some instances, however, it is beneficial to be able to leave a pressure sensitive adhesive in place for at least several days, or perhaps a week. The development of such adhesives has been more difficult. The adhesive must bond to the skin with sufficient strength that the adhesive will remain in place for a number of days, without becoming loose or “creeping” along the skin surface, yet the composition must be removable at will without causing undo skin irritation. If the pressure sensitive adhesive is being used in a transdermal patch to deliver a therapeutic agent, the visco-elastic properties of the adhesive can be affected or compromised by the nature of the drug(s) or therapeutic agent(s), solvent(s) or excipient(s) in the composition being released to the skin. Although several long term adhesive products are commercially available, further improvements are sought.